Melting Sea Ice Could Decimate Emperor Penguins

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Emperor penguins depend on the sea ice that rings the continent
of Antarctic, so it's no surprise that global warming, which is
expected to melt some of that ice, may be bad news for these
flightless, 4-foot (1.2-meter) tall birds.

Since detailed information on most colonies is not available, the
research focused on one well-studied colony of emperor penguins,
at Terre Adélie in East Antarctica, to get an idea of what might
happen to emperor penguins over
the course of this century.

Their results aren't reassuring; they project this colony is
likely to decline from 3,000 breeding pairs to 575 by 2100, a
potentially "huge decline," said lead researcher Stéphanie
Jenouvrier, a biologist at the Woods Hole Oceanographic
Institution.

Sea ice is important for penguins and for other things living
around Antarctica. For instance, krill, the tiny shrimplike
animals that penguins and other animals eat, feed on algae that
grow on the underside of sea ice. What's more the
penguins raise their young on the ice during the harsh
Antarctic winter. However, this makes getting close enough to the
birds to study difficult for scientists.

In work published in 2009, researchers with the British Antarctic
Survey used satellite images to identify 38 locations with
colonies around the continent by looking for the stains the
emperor penguins' droppings left on the white ice.

While
sea ice in the Arctic has receded to new lows in recent
years, the dynamics are different at the southern end of the
planet. The West Antarctic Peninsula, which juts north, has
warmed rapidly. And one emperor penguin colony, historically
located on Emperor Island in the peninsula's Dion Islands,
appears to have disappeared entirely.

However,
shrinking sea ice is not the case for all of Antarctica's
waters, but, ultimately, global warming is expected to shrink
Antarctic sea ice significantly.

The current research focused on a colony of penguins at Terre
Adélie. It is located near a research station making it possible
for scientists to make detailed observations of the birds every
winter since in 1962.

Based on observations at this colony, Jenouvrier and colleagues
developed a mathematical model describing the population dynamics
of emperor penguins, factored in the effects of sea ice and
looked at how climate change may affect the penguins' numbers
using
a series of climate models.

They produced a wide range of results. At one end, the
projections showed the complete loss of the penguins before the
end of this century; the most optimistic projection predicted an
increase in population until just before 2080 and a sharp
decrease the last decade or so of the century.

The median, or middle, projection, however, estimated a decline
to 575 breeding pairs by 2100.

"Overall, the ensemble of models predicts that population
declines are far more likely than population increases. We
conclude that climate change is a significant risk for the
emperor penguin," the researchers write of their results detailed
today (June 20) in the journal Global Change Biology.